The visual "mobiles" attached to infant cribs are devices designed to provide the infant with visual stimulation. There are no devices currently on the market that provide infants with complex and interesting auditory stimulation. Yet, studies by this research team show that very young infants have a keen sense of hearing and are capable of discriminating fine differences in complex sounds such as speech. More importantly, our work suggests that infants like listening to speech, particularly when in conforms to the kind of speech that is addressed to them by caretakers. The particular kind of speech has many special properties, and has been given the name "Motherese." Our laboratory research indicates that infants prefer to listen to Motherese over the kind of speech that is addressed to adults. Phase-I research examined the feasibility of creating an "Auditory Mobile" for infants, a device that presents Motherese and other complex signals that mimic its salient acoustic characteristics to infants. We made substantial progress toward establishing the technical feasibility and marketability of such a product. Moreover, a large toy company expressed a firm interest in the commercialization of the "Auditory Mobile" and two other inventions that stimulate the auditory sense -- the "Sound Maker" and the "Sensory Jack." This Phase-II proposal requests support for: (1) research identifying the parameters of the auditory signals that should be contained in these products, and (2) work on the technical solutions involving complex signal processing required by these devices.